<h3>@../index</h3>
{{#each list}}
    <dl>
        <dt>年级-{{@index}}</dt>

        {{#each .}}
            <dd>
                
                teacher:{{this.teacher}},
                number:{{this.number}}
            </dd>
        {{/each}}

    </dl>
{{/each}}

<hr>
<h3>../../</h3>
{{#each list as |grade|}}
    <dl>
        <dt>Grade:{{@index}}</dt>
        {{#each grade as |info|}}
            <dd>
             
                Teacher:{{info.teacher}},
                Number:{{info.number}}
            </dd>
        {{/each}}

    </dl>
{{/each}}

<hr>
<h3>@key / .</h3>
{{#each list}}
    <dl>
        <dt>Grade:{{@index}}</dt>
        {{#each .}}
           <dd>{{@key}}:{{this.teacher}}</dd>
        {{/each}}
    </dl>
{{/each}}

<hr>
<h3>循环空数组:</h3>
1.长度为0:{{list1}}<br>
<ul>
{{#each list1}}
    <li>{{.}}</li>
{{else}}
    <li>No data</li>
{{/each}}
</ul>

2.长度为3，元素为空:{{list2}}<br>
<ul>
{{#each list2}}
    <li>{{.}}</li>
{{else}}
    <li>No data</li>
{{/each}}
</ul>


3.长度为3，元素undefined:{{list3}}<br>
<ul>
{{#each list3}}
    <li>{{.}}</li>
{{else}}
    <li>No data</li>
{{/each}}
</ul>


4.长度为4，元素为假值:{{list3}}<br>
<ul>
{{#each list3}}
    <li>{{.}}</li>
{{else}}
    <li>No data</li>
{{/each}}
</ul>